Google's Did you mean tool is an extremely useful way to check whether or not you've spelled a word correctly. Though you can't use Did you mean to spell-check an entire document, it comes in handy for individual word lookups when you're writing in a web-based interface, such as your blog's editor, without spell checking functionality - or for acronyms, or proper names that don't appear in your spellchecker's dictionary.

For example, if I type in arguementative, it returns: Did you mean: argumentative. Simple, yet effective. — Joe Anderson